Ketanserin is –
Correct Answer: 5-HT2 antagonist
Description: Ans. is 'b' i.e., 5-HT2 antagonist o Ketanserin and ritanserin are useful as antihypertensive agents. It is important to know that these drugs have additional a receptor blocking property and antihypertensive effect is due to a-blockade, not due to 5HT2A/2C blockade.SEROTONERGIC RECEPTORSo There are four families of 5-HT receptors -5HT1, 5HT2, 5HT3, 5HT4-7o All 5-HT receptors (except 5-HT3) are G protein coupled receptors. 5 HT3 is a ligand gated cation Na+, K+) channel - ionotropic receptor.1. 5HT1 (Five subtypes 5HT1A,B,D,E,F)o All types of 5-HT1 receptors inhibit adenylyl cyclase.o These receptors function primarily as autoreceptors in brain - inhibit 5-HT release or firing of 5-HT neurons.o The most important locations of 5HT1A receptor are raphe nuclei of brainstem and hippocampus.o Buspiron, ipsapirone, gepirone (antianxiety drugs) act as partial agonists on 5HT1A receptors.o 5HT1D regulates dopamenergic tone in substantia nigra basal ganglia.o 5TH1B/1D cause constriction of cranial blood vessels,o The antimigraine drug sumatriptan is a selective 5-HT1B/1D agonist.2. 5-HT2o Coupled to phospholipase lc' and function through IP3/DAGo 5 HT2A is the most widely expressed postjunctional 5-HT receptor.o 5HT 2A/2C receptor is responsible for most of the direct action of serotonine.o Important antagonists of these receptors are : -Ketanserin and ritanserin are useful as antihypertensive agents. It is important to know that these drugs have additional a receptor blocking property' and antihypertensive effect is due to a-blockade, not due to 5HT2A/2C blockade.Clozapine, resperidone are used as antipsychotics.Methylsergide is used in migraine.Cyproheptadine blocks 5HT2A, HI histaminic and muscarinic receptors. It increases appetite and can be used in children to promote weight gain.3. 5-HT3o It is the only 5-HT receptor which is a ligand gated cation Na+, K+ channel.o It mediates most of the indirect and reflex actions of 5-HT at:1. Area postrema and nucleus tractus solitarius in brain stem - nausea and vomiting.2. Nerve ending in myentric plexus - | peristalsis3. Somatic and autonomic nerve ending - pain, itch, coronaiy chemoreflex.o Stimulation of 5-HT3 receptor is responsible for vomiting induced by anticancer drugs.o 5-HT3 receptor antagonists (ondansetron, granisetron and tropisetron) are DOCs for chemotherapy induced vomiting.4. HT4o Present on mucosa, plexuses and smooth muscles of the gut - | intestinal secretion and peristalasis.o Cisapride, renzapride and tegaserod are selective 5-HT4 agonists - useful in gastroesophageal reflux disease.o Most direct actions of serotonin are mediated by 5 - HT2 receptors.o Most indirect and reflex actions of serotonin are mediated by 5-HT3 receptors.
Category:
Pharmacology
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